Tube Sheet Assembly for a Heat Exchanger

ABSTRACT

A tube sheet assembly for a heat exchanger is disclosed. The tube sheet assembly includes a plastic sheet having multiple tube-retention holes defined therein and a metal plate having multiple holes defined therein, each hole being substantially coaxial with a corresponding tube-retention hole of the plastic sheet. The metal plate is connected to the plastic sheet. The metal plate can be fabricated of, for example, steel or other metals. The plastic sheet can be fabricated of, for example, nylon, ultra-high-molecular-weight polyethylene, or polytetrafluoroethylene. Tubes can be disposed in the tube-retention holes of the plastic sheet and the holes of the metal plate. In an example, the tube-retention holes of the plastic sheet have a smaller diameter than the holes of the metal plate and the tubes contact the plastic sheet without contacting the metal plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/103,852, filed on Jan. 15, 2015, now pending, the disclosure of whichis incorporated herein by reference.

FIELD OF THE DISCLOSURE

The disclosure relates to heat exchangers.

BACKGROUND OF THE DISCLOSURE

A heat exchanger is designed to transfer heat from one medium toanother. Heat exchangers generally have several tubes to carry one ofthese media, and the design often includes where the tubes pass throughheaders or other plates. These headers or other plates can be used to,for example, separate or position the tubes within the heat exchanger.

Headers and plates that position the tubes are usually fabricated ofmetal. This presents multiple problems. First, the header or plate mayhave a different coefficient of thermal expansion than the tubes, whichcan lead to stress or damage on the components due to expansion orcontraction. Second, the header or plate can cause abrasion to the tubesduring installation as the tubes are moved into position through theplate or header. Third, the header or plate can be expensive dependingon its thickness or dimensions.

A common technique for mitigating the above problems is through the useof a ferrule around each tube and at each tube-to-header interface. Inthis way, the ferrule can prevent damage to the tube due to expansion,contract, abrasion, etc. However, the use of ferrules can significantlyincrease the cost of the resulting heat exchanger in both materials andlabor in assembly.

BRIEF SUMMARY OF THE DISCLOSURE

A tube sheet assembly for a heat exchanger is disclosed. The tube sheetassembly includes a plastic sheet having multiple tube-retention holesdefined therein and a metal plate having multiple holes defined therein,each hole being substantially coaxial with a correspondingtube-retention hole of the plastic sheet. The metal plate is connectedto the plastic sheet. The metal plate can be fabricated of, for example,steel or other metals. The plastic sheet can be fabricated of, forexample, nylon, ultra-high-molecular-weight polyethylene, orpolytetrafluoroethylene. Tubes can be disposed in the tube-retentionholes of the plastic sheet and the holes of the metal plate. In anexample, the tube-retention holes of the plastic sheet have a smallerdiameter than the holes of the metal plate and the tubes contact theplastic sheet without contacting the metal plate.

DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the disclosure,reference should be made to the following detailed description taken inconjunction with the accompanying drawings, in which:

FIG. 1A is a side elevation view showing an example of a header plateand tubes according to an embodiment of the present disclosure;

FIG. 1B is a detail view of a portion of the header plate and tubes ofFIG. 1A;

FIG. 2 is a perspective view of tube sheet assembly in accordance withanother embodiment of this disclosure;

FIG. 3A is an exploded perspective view of the tube sheet assembly ofFIG. 2;

FIG. 3B is a detail view of a portion of the tube sheet assembly of FIG.3A; and

FIGS. 4A and 4B shows an embodiment of this disclosure in which tubesare inserted through the tube sheet assembly.

DETAILED DESCRIPTION OF THE DISCLOSURE

Although claimed subject matter will be described in terms of certainembodiments, other embodiments, including embodiments that do notprovide all of the benefits and features set forth herein, are alsowithin the scope of this disclosure. Various structural, logical,process step, and electronic changes may be made without departing fromthe scope of the disclosure.

The presently-disclosed tube sheet assembly is used in a heat exchangerto position or separate tubes that carry a heat transfer medium. Thetube sheet assembly may be used as a header plate, such as thatillustrated in FIG. 1, or other plates that position tubes in the heatexchanger. Multiple tube sheet assemblies can be used in a single heatexchanger.

As seen in FIGS. 2, 3A, and 3B, an embodiment of the presently-disclosedtube sheet assembly 10 includes a plastic sheet 12 having a plurality oftube-retention holes 20 defined therein. Each tube-retention hole 20 hasa diameter which is substantially the same as an outside diameter of aheat-exchanger tube 13. In some embodiments, substantially similardiameters provides that the tube may be inserted through eachtube-retention hole 20, while still being held stationary in atransverse direction within the hole 20.

The tube sheet assembly 10 further includes a metal plate 11 has aplurality of holes 22 defined there, each hole 22 substantially coaxial(as further defined below) with a corresponding tube-retention hole 20of the plastic sheet 12. Each hole 22 of the metal plate 11 has adiameter which is greater than the diameter of the tube-retention holes20 of the plastic sheet 12. Tubes 13, which may be copper, aluminum,alloys thereof, or other materials, can be passed through the tube sheetassembly 10. The centers of the holes in the plastic sheet 12 and metalplate 11 may be aligned (i.e., coaxial). In other embodiments, thetube-retention holes 20 of the plastic sheet 12 are not coaxial with theholes 22 of the metal plate 11, although the tube-retention holes 20 maybe configured such that a tube 13 disposed through a tube-retention hole20 of the plastic sheet 12 and a corresponding hole 22 in the metalplate 11 is not in contact with the metal plate 11 (i.e., the holes 20,22 are considered to be “substantially coaxial”). The tube-retentionholes 20 of the plastic sheet 12 and the holes 22 metal plate 11 may bethe same diameter or different diameters. In some embodiments, thetube-retention holes 20 in the plastic sheet 12 may have a smallerdiameter than the holes in the metal plate 11.

The plastic sheet 12 may be fabricated of nylon,ultra-high-molecular-weight polyethylene, polytetrafluoroethylene, orother materials. The plastic sheet 12 may be softer and/or more flexiblethan the metal plate 11.

The metal plate 11 may be fabricated of steel or other materials. Forexample, stainless steel or zinc-plated steel (i.e., galvanized steel)may be used. This metal plate 11 provides support for the plastic sheet12 and prevents the plastic sheet 12 from drooping, warping, sagging, orotherwise moving out of a desired position.

The plastic sheet 12 and metal plate 11 are connected to one another.For example, the plastic sheet 12 and the metal plate 11 may beconnected using fasteners such as pop rivets, bolts, screws 24, or otherdevices known to those skilled in the art. In other embodiments, theplastic sheet 12 and metal plate 11 may be connected using an adhesive.Other techniques for connecting the components can be used.

In an embodiment, the tubes contact the plastic sheet 12 withoutcontacting the metal plate 11 when assembled. FIGS. 4A-4B illustrate thetube sheet assembly from both the side of the plastic sheet 12 (FIG. 4B)and the metal plate 11 (FIG. 4A). The tube sheet assembly of FIGS. 4A-4Bcan correspond to the tube sheet assembly 10 in FIGS. 2 and 3. Theplastic sheet 12 is illustrated as white in FIGS. 4A-4B. As seen inFIGS. 4A-4B, the tubes contact the plastic sheet 12 and not the metalplate 11. As shown in FIG. 4A, there is a gap between the exterior ofthe tubes and the circumference of the holes in the metal plate 11. Theholes in the metal plate 11 are larger in diameter than thecorresponding holes in the plastic sheet 12. The diameter of the holesin the plastic sheet 12 may be approximately the same as the outerdiameter of the tubes. In various embodiments, the diameters may differto provide, for example, ease of installation, proper positioning,friction fit, or a desired amount of expansion or contraction.

The tube sheet assembly 10 enables movement of the tubes 13 through theplastic sheet 12 without damage or wear to the material of the tubes 13due to the flexible or yielding nature of the plastic in the plasticsheet 12. Furthermore, the plastic sheet 12 allows the tubes 13 toexpand during operation without causing damage or wear due to theflexible nature of the plastic. Minimizing or eliminating contactbetween the tubes and the metal plate 11 reduces or eliminates thepossibility that the heat exchanger tubes will be worn through due tovibration. The plastic sheet 12 is less expensive than the metal plate11, so the combination of the plastic sheet 12 and metal plate 11 lowersthe overall material cost of the tube sheet assembly 10 compared to onemade of only metal. Ferrules can be avoided through use of the plasticsheet 12. Removing ferrules eliminates rattling where tubes vibrateagainst the ferrule and tube sheet assembly. Use of the plastic sheet 12also eliminates known issues related to a bi-metallic interface when twodifferent metals are used for the tubes and for the metal plates inprevious designs.

Although the present disclosure has been described with respect to oneor more particular embodiments, it will be understood that otherembodiments of the present disclosure may be made without departing fromthe spirit and scope of the present disclosure. Hence, the presentdisclosure is deemed limited only by the appended claims and thereasonable interpretation thereof.

what is claimed is:
 1. A tube sheet assembly for a heat exchanger,comprising: a plastic sheet having a plurality of tube-retention holesdefined therein, wherein each tube-retention hole has a diametersubstantially the same as an outside diameter of a heat-exchanger tube;and a metal plate attached to the plastic sheet, the metal plate havinga plurality of holes defined therein, each hole coaxial or substantiallycoaxial with a corresponding tube-retention hole of the plastic sheet.2. The tube sheet assembly of claim 1, wherein the metal plate isfabricated of steel.
 3. The tube sheet assembly of claim 1, wherein theplastic sheet is fabricated of nylon, ultra-high-molecular-weightpolyethylene, or polytetrafluoroethylene.
 4. The tube sheet assembly ofclaim 1, further comprising a plurality of heat-exchanger tubes disposedthrough the holes of the plastic sheet and the holes of the metal plate.5. The tube sheet assembly of claim 4, wherein the holes of the plasticsheet have a smaller diameter than the holes of the metal plate.
 6. Thetube sheet assembly of claim 5, wherein the tubes contact the plasticsheet and do not contact the metal plate.